Rendering

CSR

The server sends a near-empty HTML shell and JavaScript builds the whole page in the browser.

This is the classic single-page-app approach: the browser downloads a JavaScript bundle, runs it, fetches data, then paints the UI. Navigation feels instant once it's loaded, but the first paint is slow and crawlers historically saw an empty shell, which hurts SEO. Analogy: you're handed flat-pack furniture and assembly instructions instead of an assembled chair. It's the right call for things like a dashboard behind a login, where SEO doesn't matter and you want app-like interactivity.